The clinical efficiency of an occulusal splint in TMJ dysfunction is well known, but the precise mechanism of the action remains to be elucidated. To test the hypothesis that a stabilization splint is useful in the modified mandibular position, we observed variation of the tapping point as the terminal position of the mandibule during open-close movement, when subjects wore the splint and after they removed it.
The subjects were classified into two groups. Six healthy volunteers with normal occulusion were selected as the control group, and another 6 volunteers with unstable occulsion, and few signs or symptoms of TMD, were selected as the inapparent TMD group. The movement of the mid-incisal point was recorded by six degrees of freedom, using a new analyzing system for stomatognathic functions, during tapping movements for 30 seconds. All subjects wore a maxillary splint.
The following four experimental conditions were used:
Natural tooth tapping (N. T. I), tapping with the splint just after putting it in the mouth (I. S. ), tapping with the splint after wearing it for 3 hours (A. S. ), and tapping after the splint had been removed (N. T. II).
Tapping points were measured using a signal processing software (AcgKnowledge^®) and Variance (Var) of tapping points on three-dimensional coordinates.
When we compared Var in the horizontal plane, the value in the antero-posterior (AP) direction was significantly larger than that in the lateral direction. When we compared between N. T. I and N. T. II, Var of N. T. II in the AP direction is smaller than that of N. T. I.
The value of N. T. II for the inapparent TMD group was significantly lower than that of N. T. I.
These results suggest that a stabilization splint can reduce Var in TMD patients.

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A jaw function tracing device (Gnathohexagraph^®) that can be adapted to comparatively easy has been coming into wide use recently. The way of inputting an option point, a measurement error by 3 dimension coordinate, the propriety of the clinical application to the child were examined. If penpointer was not turned in front of the CCD camera, the mistake of the coordinate was easily made in the case of the input of the option point. As for the measurement precision, a measuring error was less than 1% respectively by 3 dimension coordinate. And, it was shown by the clinical result applied fully as for pediatric dentistry as well.

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The purpose of this study was to evaluate the signal intensity of the posterior disc attachment on T1-weighted magnetic resonance imaging (1.5 Tesla) before and after arthroscopic lysis and lavage in patients with temporomandibular disorders.
Forty three joints (43 patients) that were unresponsive to nonsurgical therapy, and that had undergone arthroscopic lysis and lavage, were included in this study. The patients were classified into 2 groups, as follows: a successful group (32 joints of 32 patients) and an unsuccessful group (11 joints of 11 patients). We compared the signal intensities of the posterior disc attachment before and after arthroscopic lysis and lavage.
In the successful group, there was a significant association between before and after arthroscopic lysis and lavage, in the change of the signal intensity in the posterior disc attachment, whereas no statistical difference was found in the unsuccessful group. The incidence of low signal intensity in the posterior disc attachment was higher in the successful group (81.3%) than in the unsuccessful group (45.5%).
These results suggested that the improvement of joint pain and dysfunction after arthroscopic lysis and lavage was correlative to low signal intensity in the posterior disc attachment.

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Some studies show that people with a steep articular eminence of the temporomandibular joint (TMJ) were more likely to have articular disc displacement (DD), while other studies failed to prove this phenomenon. It has also been suggested that flattening of the articular eminence is caused by DD. To resolve this controversy, we studied TMJ MR images obtained from teens, who would not have a long history of DD. The purpose of this study was to evaluate the hypothesis that a steep articular eminence is a predisposing factor for DD. Saggital MR images of 51 TMJs, obtained from 29 patients with TM disorder, and 38 TMJs obtained from 19 asymptomatic volunteers, were used in this study. Three images: lateral, central, and medial, from each joint, were assessed. Cases with any deformity of the disc or condyle were excluded from this study. Morphology of the articular eminence was classified into three types according to Kurita et al. 's classification: box (steep posterior slope of the eminence), sigmoid (S-shaped slope), and flat (shallow eminence) types. The relationship between the types of eminence configuration and the presence of DD was tested using the Chi-square test for 1×m contingency table. In the central and medial images, the box type of configuration was more significantly seen in the TMJs with DD than in the TMJs without DD (p<0.05). We conclude that the configuration of the articular eminence is an important anatomic factor of DD. Moreover, a steep articular eminence would be a predisposing factor for DD.

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We report on three newborn babies with temporomandibular joint (TMJ) clicking.
Case 1: A 5-day-old girl was referred to our clinic for examination of TMJ clicking. Her mother noticed bilateral TMJ clicking during nursing. The infant could open her mouth normally and did not seem distressed by the clicking or by palpation. Radiographs were normal. No treatment was performed. The TMJ clicking disappeared within 40 days.
Case 2: A 23-day-old boy with right TMJ clicking, that was noticed by his mother after the beginning of nursing, was referred to our clinic. The clicking occurred during mouth opening and closing. There was no other abnormality. He had no difficulty nursing and had grown well, so no treatment was performed.
Case 3: We examined a three-month old girl with bilateral TMJ clicking. Soon after her birth, she was noticed to have TMJ clicking when her mandible protruded, and the sound had continued for three months. The clicking was also detected during mouth opening by palpation. She seemed to have no limitation of mouth opening, TMJ pain, or abnormal development. She was treated by observation only.
Little is known about TMJ clicking of newborns at present, and further reports and examinations will be needed.

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In general, temporomandibular joint (TMJ) ankylosis occurs in childhood as a result of inflammation and/or trauma around the TMJ. This ankylosis, with limitation of the range of motion, inhibits mandibular growth gradually. In this presentation, we report a case of TMJ ankylosis that was managed for a long time after surgical mandibular mobilization. The patient was a girl of age 5 years and 3 months, with trismus and jaw asymmetry. She had a history of trauma to her mental region at age 17 months. Her mother had noticed her trismus at one year after the trauma. At the first visit, the range of mouth opening was only 5mm at the interincisors, and it was deviated 3mm to the left. On CT appearances, the left condylar head of the mandibular bone and mandibular fossa of the temporal bone were morphologically changed to an irregular radio-opaque mass. We performed an arthroplasty on the mandibular ramus, to get the enough movement of the mandible, at the age of 5 years and 8 months. As a result of long-term management after the arthroplasty, we gained some findings, as follows: 1. Asymmetry of the mental region of the mandible was increased to the left within a year after surgery. 2. The range of motion of the mandible was also increased, to approximately 30mm, within a year, and after that asymmetry of the mental region was almost stable. We think the mandibular growth of the left side was gradually improved to some degree because of the jaw function. 3. On CT appearances before her orthognathic surgery, bony fusion between the condylar head and the mandibular fossa was revealed. 4. There has been no abnormal finding morphologically and functionally on her right TMJ.

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Purpose: A simplified three-dimensional finite element model of the mandible, including the temporomandibular joint (TMJ), was developed, to examine the influences of changes in anatomical morphology on TMJ loading. The purpose of this study was to investigate the validity of the simplified model.
Materials and Methods: Based on a young human dry skull, a numerical model of the mandible, including the TMJ, was developed. In this model, the mandible excepted the ramus of mandible, and the condyle was connected with the body of mandible using rigid elements. Contact elements allow slip and separation effects between the contact surface of the articular disk and the articular surface of the condyle or eminence. The magnitude and direction of the condylar displacement during clenching were measured by changes in the occlusion.
Results: 1. In bilateral occlusion, bilateral condyles moved forward and upward.
2. In unilateral occlusion, the balancing side condyle moved forward, upward, and inward. The working side condyle moved forward, upward, and outward, except for the unilateral 2 nd molar occlusion where the working side condyle moved backward, downward, and outward.
Conclusions: The direction and magnitude of the condylar displacement were analogous to those of previous studies. This suggested that the simplified three-dimensional finite element model adopted in the present study may be useful in analyses of the TMJ.

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A 24-year-old woman was treated orthodontically after her reduced fixation of the fractures of bilateral mandibular necks and mandibular body caused by a traffic accident. At the same time, functional analysis, such as jaw movement analysis using Computer Axiograph (CADIAX^®), was also done, at our university hospital. She showed severe open bite just before our orthodontic treatment, because of distortion of mini-plates put in place by a plastic surgeon and shortening of condyle necks after surgical operation. Our orthodontic treatment with a multi-bracket system continued for approximately 20 months.
We obtained a good intraoral clinical result after our orthodontic active treatment. She showed better alignment of teeth, better incisal inclination, better overbite, and better occlusion. However, functional recovery, checked by jaw movement analysis by Computer Axiograph, needed two more years after orthodontic treatment.

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It is reported that an osteoarthritic/osteoarthrotic (OA) change of the mandibular condyle is frequently observed with progression of internal derangement of the temporomandibular joint (TMJ). Condylar OA change is usually evaluated using lateral X-ray images of the TMJ. Previously, we reported that resorption of the lateral pole (postero-superior aspect of the lateral pole) of the mandibular condyle (RLC) was frequently observed in joints with disk displacement. The purpose of this study is to analyze the relationship between RLC and the OA change, which was observed in lateral images of the mandibular condyle (sagittal OA change).
RLC was assessed on plain radiographs of transorbital projection, in 217 TMJs out of 138 patients. Displacement of the TMJ disk and the sagittal OA change were assessed using MR imaging at the representative center depth of the TMJ.
It was considered that the concurrent rate of both RLC and a sagittal OA change was 28 percent. In the joints with anterior disk displacement with reduction, RLC or a sagittal OA change tended to be observed solely. And in the joints with anterior disk displacement without reduction, both changes tended to be increasingly observed at the same time.
The results of this study suggest that both RLC and a sagittal OA change may be frequently observed with advancing TMJ internal derangement. However, it is thought that RLC or a sagittal OA change develop separately by different mechanisms.

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A comparison between medial and lateral disk attachments in a rabbit regarding the ultrastructure and mechanical properties was carried out. The fiber structures of the disk attachment were examined by light microscopy (LM) and scanning electron microscopy (SEM), while mechanical properties were investigated by a tensile tester. As a result, collagen fibrils were found running anteroposteriorly in medial fiber disk attachment, and medially in lateral fiber disk attachment. This finding was more prominent in elastic fiber. Three-dimensional organization of collagen fibrils showed various configurations, such as wavy, canvas jacket-like, spiral, and others. Every finding indicated both extensibility and strength. Regarding mechanical property, no statistical differrences were found in stain and elasticity between medial and lateral disk attachment, except the strain at failure, which showed a significant difference (P<0.05).

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